Okay, when you get to the manual section of the ubuntu feisty install. Delete that 8gb partition you made, now select the freespace it should be saying something like... "Free Space 8XXXmb" (something like that, if you made an 8gb partition) Subtract 256mb from that number then select it and create new partition and use that number minus the 256mb, chose ext3 as file structure and then mount point of "/" now click okay. Now you'll see "Freespace 256mb" select that and create a new partition and it's file structure or whatever make it "swap"
I forgot what everything is actually called, i don't remember if that drop down menu is in fact called "File Structure" But I hope you at least kind of understand that.. heh I'm terrible at creating instructions from memory =S
But that should work!